The influence on loading rate on pile behaviour in fine grained soils

Statnamic Testing was jointly developed in the early nineties by Berminghammer Foundation Equipment of Canada and TNO Building and Construction Research of the Netherlands as an alternative method of pile load testing. The system is a kinematic or rapid load test, increasingly being used as an alternative to dynamic testing in the USA, East Asia and more recently in the UK (Anon, 1997).
To derive static pile load deflection data it is necessary to analyse the Statnamic data to account for pile/soil inertia and damping effects. The most commonly adopted method is referred to as the Unloading Point Method. This method of analysis provides excellent correlation with static tests for sands and gravels (Brown, 1994), but may over-predict pile capacities by up to 30% for fine grained soils (clays).
Current understanding of the Statnamic test is based upon field studies that are influenced by natural soil behaviour. Thus model pile testing in a clay calibration chamber is being undertaken at the University of Sheffield (Anderson et al, 1991). Results from these tests will be used to determine the effect of the rate of testing on pile bearing capacity, and will govern the design and testing procedure for a full scale field study.